Singer, songwriter and producer Matthew Koma collaborated with uber-producer Zedd on such hits as “Spectrum” and “Clarity”, which came out in 2012 and 2013 respectively, but the pair haven’t worked together since.

Thanks to a lengthy statement Koma posted on Instagram Wednesday, we now know why, with Koma alleging Zedd (whose real name is Anton Zaslavski) took all the credit for his work.

“In response to years of: ‘What happened with you & Zedd.’ I want to finally be transparent about this… it’s a really sad truth because I’m extremely proud of the work he and I did together… unfortunately my good feelings toward those songs have all but disappeared as they were experienced alongside someone so toxic and self serving that it occupied the space where any happiness could exist,” wrote Koma, who is engaged to actress Hilary Duff.

“I wrote every word and melody,” says Koma of their collaborations, claiming that “I was just brushed under the rug while he took all the credit, which felt confusing because the millions of people who connected to ‘Clarity’ and those other songs, seemed to connect to the lyrics/emotion/melodies I had written. But he deemed his Kick Drum sound the driving force and left me out of all shared credit.”

According to Koma, “s**tty people suck and when they’re successful people are afraid to blow the whistle,” noting that he’s since encountered other people who’ve worked with Zedd and come away with similar experiences.

“For years I thought maybe it was me, but over time, I’d run into other people who worked with him — other writers/singers/producers/DJs/People on his own team… and the sentiment was shared. He’s the worst,” Koma, 32, continued.

Dubbing Zedd “toxic” and “abusive,” Koma added: “But for those always wondering why there was never more music from the two of us, it wasn’t really my choice. Now, he has plenty of people to write his songs and produce his tracks and help him continue on his trajectory. But I [would] rather work at Starbucks and clean the toilets than ever experience that abusive dynamic again. Toxicity doesn’t breed happiness.”

Koma’s fiancee, Hilary Duff, commented to his post. “This is so important for people who love the music to know. Writers are taken advantage of, ignored, and mistreated. Proud of you for finally speaking up,” she wrote.

Singer Bebe Rexha also commented, writing: “The unfortunate dark side of the music business.”

In addition, actor Christopher Mintz-Plasse (“SuperBad”) wrote a comment: “Hell yes. Get the word out man. Can’t get treated that way.”

Zedd has since released a lengthy statement on Twitter.

The message included, “What hurts the most is that Matt feels underappreciated and treated unfairly while I have countless times mentioned him (or) his name, while we’ve done promo together, performed our songs live together and I thought I was being supportive.

“Anywhere you look, you will see Matt credited for his work. I wish he would have just let me know in person what he was feeling. I never want anyone I work with to be unhappy. I treat everyone I work with with love and respect and it hurts me to see someone feeling differently after seven years.”

Zedd concluded, “What I told Matt doesn’t change – I am incredibly proud of our work together and I continue to wish him nothing but the best. Hopefully one day we can sit down together again as friends.”